obama-care doesn't make it less expensive. >> reporter: he wants obama-care gone, including the prescription drug benefit for seniors. but he does want to keep one of the most popular pieces of obama-care although he doesn't say exactly how his plan will work. >> we have to make sure people with pre-existing conditions can get insured and folk that get sick don't get dropped by their insurance company. >> reporter: romney and paul ryan plan to cap malpractice insurance. cut medicaid by $810 billion over the next ten years, give states more control over their medicaid funds and overall mediocri medicare. overhaul, people up to age 55 would get a voucher to purchase private insurance or they can stick with traditional medicare. >> this financial support system is designed to guarantee that seniors can always afford medicare coverage, no exception exceptions. >> those are some major differences between the candidates. perhaps the biggest split is over medicaid, not medicare, medicaid, what most people consider the safety net for america's poorest. let's bring in our chief medical correspondent